There is provided a metal-based particle assembly comprising 30 or more metal-based particles separated from each other and disposed in two dimensions, the metal-based particles having an average particle diameter of 200 to 1600 nm, an average height of 55 to 500 nm, and an aspect ratio of 1 to 8, wherein the metal-based particle assembly has in an absorption spectrum for a visible light region a maximum wavelength of a peak at a longest side in wavelength, and the maximum wavelength shifts toward a shorter side in wavelength in a range of from 30 to 500 nm as compared with that of a prescribed reference metal-based particle assembly. The metal-based particle assembly can have in an absorption spectrum a maximum wavelength of a peak at a longest side in wavelength, and the maximum wavelength is in a range of from 350 to 550 nm.